Casting # Question

[tk4td40]

I recently came across a 72' Corvette Engine (350 CI. Block Casting # 3970010) and the Head Casting # 3973487X. My Question is Does Anyone know what the "X" stands for. Any Help would be of great help.

Thank you for your Time,

TK

 

[67HEAVEN]

Apparently the 3973487X heads had slightly larger intake ports than the 3973487.

 

[Tom73]

I just looked on the Mortec site, www.mortec.com, and it appears that the 3973487 heads were used on the LT1 engines and the 3973487X heads were used on the other engines. Same size chambers, so would assume a difference in valve sizes with the "x" heads having smaller valves then the LT1 heads.

tom...

 

[Jack]

my L48 came with 487 ... not 487X

I just looked on the Mortec site, www.mortec.com, and it appears that the 3973487 heads were used on the LT1 engines and the 3973487X heads were used on the other engines. Same size chambers, so would assume a difference in valve sizes with the "x" heads having smaller valves then the LT1 heads.

tom...

When I pulled my 71 base L48 apart it was clear it was an original motor. The heads were both 487 ... not 487X. My 487 heads' valves are 1.94" intakes & 1.50" exhausts. In summary, my 71 base L48 came with small valve 487 heads ... not 487X. I dunno what if any difference there is between 487 & 487X castings.
JACK:gap

 

[mike weyman]

i'm told x head had 202/1.6 valves. the lt1 my not have needed bigger valves for the combo.mike

 

[curtis]

The circle track guys around here just drool all over themselves when they see 487x heads. They claim they are the best flowing GM iron heads they are allowed to run. Humps and vortecs are out for these guy's classes.

 

[tk4td40]

Just wanna Thank you all for posting a reply. What Im hearing is the 487X has the bigger Valves. Again I wanna say thanks to all of you (Thank You!).

PS If you find any more info on them please post it.

Thanks Again,

TK

 

[Tom B Hargrove]

The heads on my original 72 350 200hp(standard) engine are 487x heads. They still have the small valves in them that came from Chevrolet. I have a 72 camero that has 487 heads, and it has small valves also. I can find no difference in them at all. I've never found anyone that can tell me what the difference is. I heard that the 487x heads had hardened seats in them, but I couldn't tell if they are. The 487's seats look just like the 487x's. Tom

 

[67HEAVEN]

Online references........for what they're worth:

[font=Verdana, Arial, Helvetica, sans-serif][size=-1]LARGE CHAMBER PRODUCTION "ON CAR" HEADS[/size][/font]
[font=Verdana, Arial, Helvetica, sans-serif][size=-1]"487" – 3973487, OR 3973487X. The regular casting was found on the 1971-1972 350 LT-1 engines, had 1.94/1.50" valves, 76CC combustion chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's. The 487X had 2.02/1.60" valves.[/size][/font] http://www.chevytalk.com/tech/engine/SBC_Heads.html

3973487 350 71-76 71-72 LT1, 75cc, 161/65cc port volumes
3973487X 350 71-72 75cc, larger intake ports
http://www.stingray.nu/temp/heads.htm

Cylinder Head Casting Number - 3973487X 1972, 350cid, LT-1 engine with 2.02" exhaust and 1.60" intake valves, and 76CC combustion chambers. The cylinder head casting number is found underneath the rocker cover, between rocker arm pedestals.
http://www.pattson.com/maych/mh_specs.htm

 

[Jack]

Online references........for what they're worth:

Ya sure got that right about online references ... absolutely NO concensus among sites re: 487 v. 487X ... no agreement which, if either # was specific for small valves ... nor if either was specific to LT-1 .... nor if either # was specific for larger ports (larger ports & larger valves are not the same thing). In some respects, chevytalk's "bert" has gotten part of it right where his 487/X specs are "should be". Likely best info if no one really knows is "may be".
JACK:gap